Status of the Beam Method M. Scott Dewey National Institute of Standards and Technology Workshop on Next Generation Neutron Lifetime Measurements in the.

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Presentation on theme: "Status of the Beam Method M. Scott Dewey National Institute of Standards and Technology Workshop on Next Generation Neutron Lifetime Measurements in the."— Presentation transcript:

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Status of the Beam Method M. Scott Dewey National Institute of Standards and Technology Workshop on Next Generation Neutron Lifetime Measurements in the U.S.

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“Bottle” Experiments: Direct Observation of Exponential Decay: Observe the decay rate of N 0 neutrons and the slope of is Similar in principle to Freshman Physics Majors measuring radionuclide half lives -- only a lot harder. Form two identical ensembles of neutrons and then count how many are left after different times. Beam Experiments: Decay Detector Neutron Detector Fiducial Volume Neutron Beam Decay rates within a fiducial volume are measured for a beam of well known fluence.

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Two Beam Methods in Use Today Bunches of neutrons (a chopped beam) Define a measuring time during which a bunch is entirely inside the detector Measure the number of neutrons in the bunch Measure the number of decays produced during that time Continuous neutron beam Define a length of the beam to monitor Define a measuring time Measure the average density of neutrons in the beam during that time Measure the number of decays produced in that length during that time

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Setup 7 TPC in a Vacuum chamber Spin Flip Chopper In a Lead Sheald 20 cm Iron shield Gas line DAQ Inside of Lead shielding Inside of Cosmic ray Veto Set up of our experiment in “NOP” beam line. TPC in the vacuum chamber

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200820092010201120122013201420152016 MLF Power chronological table 8 嶋 TPC G10-TPC PEEK-TPC 20 kW100 kW 200 kW Earthquake 300 kW 200 kW Accident of hadron hall The first beam accept at the “NOP” Beam line 300 kW 600 kW? First detection of 3He(n,p) reaction First detection of Neutron β-decay Design the G10-TPC Design the PEEK TPC, (Low noise Amp) Development of software (Analysis framework, Geant4) Material test (PEEK) SFC shielding upgrade BG survey Development of DAQ system TPC Basic properties test Data taking2012 (commissioning) Upgrade of analysis framework for physics run Design and development of DAQ system Analysis for commissioning data Today Data Taking 2014 Design and development of Large SFC Commissioning for the new system LARGE PEEK-TPC Data taking for 1sec level Measurement of Beam profile Design and development of Large TPC 1 st JPARC symposiu m Beam intensity is estimated to be 18 times. Increasing size the Spin Flip Chopper is planed at 2014/2015. Intensity will be 18 times by a designed value. We will start physics run to 1sec at 2016/2017 2017

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Beam Halo Dysprosium imaging techniques were used to measure the neutron beam profile. 10 -3 beam fraction were found outside the active detector radius. We are re-examining the imaging process. We suspect the halo might have been over estimated. If not, we will be using larger detectors. Either way the uncertainty in halo loss for this run will be around 0.1s instead of 1s. Precision machined Cadmium mask for Dy foil in collimator mount. Nico et al Phys Rev C 71 055502 (2005) Images were taken using Cd masks to obtain sharp edges “Blooming”

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Trap Non-Linearity Trap Position L end varies with the trap length due to difference in the electrostatic potential at different radial positions and with the changing magnetic fields near the trap ends. Previously uncertainty dominated by the variation in the magnetic field for the longest trap length : Running with smaller trap lengths will eliminate the largest contribution to this systematic uncertainty, giving :

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Conclusions Two beam lifetime measurements should be forthcoming; both are aiming for 1 s uncertainties Penning trap lifetime final result: 2017? TPC beam bunch lifetime final result: 2018? Concerning the Penning trap lifetime experiment We will have nearly a year to test and debug the experiment before accepting neutrons; this is unprecedented Many of the things we will learn carrying out BL2 will guide BL3 going forward